How accurate is Invisalign in nonextraction cases? Are predicted tooth positions achieved?

Predictability of orthodontic tooth movement with aligners: effect of treatment design

BACKGROUNDS

The present study was designed to define: (1) which are the less predictable OTM with Invisalign aligners when the treatment plan is designed by expert operators, (2) if the presence and shape of attachments influence the predictability of OTM and (3) if patients' demographics influence OTM predictability. The sample comprises 79 prospectively recruited patients (mean age 30.8 years; SD 12.0; 23 M, 56 F), treated by expert operators with an average of 27 aligners (SD 15) in the maxillary arch and 25 aligners (SD 11) in the mandibular arch. Post-treatment digital models and final virtual treatment plan models were exported from ClinCheck® software as STL files and subsequently imported into Geomagic Qualify ®software, to compare final teeth positions. The differences were calculated and tested for statistical significance for each tooth in the mesial-distal, vestibular-lingual and occlusal-gingival directions, as well as for angulation, inclination and rotation. In addition, the statistical significance of categorical variables was tested.

RESULTS

The lack of correction was significant for all movements and in all group of teeth (P < 0.01) except for the rotation of maxillary first molar. The prescribed OTM, the group of teeth and movement, the frequency of aligner change and the use of attachment influence the outcome. The greatest discrepancies in predicted and achieved tooth position were found for angular movements and rotation of teeth characterized by round-shaped crowns, for a ratio of approximately 0.4° per 1° prescribed. Optimized attachments for upper canines and lower premolar rotation seem not working properly. Second molar movements are mostly unexpressed. Furthermore, changing the aligner every 14 days will reduce the lack of correction of the 12% with respect to 7 days aligner change.

CONCLUSIONS

Predictability of orthodontic movement with aligners still has limitations related to the biomechanics of the system: the shape of some attachments and the characteristics of aligner material need to be redefined. However, the results of this study allow to properly design the virtual treatment plan, revealing how much overcorrection is needed and which attachments are most effective.

The predictability of the mandibular curve of Wilson, buccolingual crown inclination, and transverse expansion expression with Invisalign treatment

INTRODUCTION

This study aimed to provide an initial investigation into the mandibular curve of Wilson (COW) handling using the Invisalign appliance (Align Technology, Santa Clara, Calif). Individual buccolingual crown inclinations and transverse expansions were also investigated to detect any regions of ineffectiveness in the dental arch.

METHODS

A retrospective sample of patients treated by an experienced Invisalign provider in private practice was used. All adult patients with Class I or II Angle malocclusions and mild to moderate crowding treated using a minimum of 14 Invisalign aligners without intermaxillary elastics, bite ramps, or auxiliaries and a nonextraction mandibular arch from 2013-2019 were selected. Dental models at the initial scan, the ClinCheck prediction, and the outcome after the initial series of aligners were analyzed with Geomagic Control X software (version 2017.0.3; 3D systems, Rock Hill, SC). The COW, buccolingual crown inclination relative to the occlusal plane and cusp tip expansion were compared between ClinCheck changes and achieved changes.

RESULTS

Forty-two subjects met the selection criteria. 74% of subjects experienced a flatter COW than ClinCheck predictions, and the mean difference was 0.76 mm (P = 0.0149). The first molars encountered 0.52 mm (P <0.001) more buccal crown inclination than ClinCheck predictions. No other teeth experienced statistically significant buccolingual inclination differences to ClinCheck. The second molars were the only teeth to experience significantly more arch expansion than ClinCheck at 0.68 mm (P = 0.0046).

CONCLUSIONS

The Invisalign appliance tended to over-flatten the mandibular COW compared with ClinCheck because of the lack of buccal root torque in the mandibular first molars during expansion. The mandibular second molars were the only teeth to experience more expansion than ClinCheck.

Changing clear aligners every 10 days or 14 days ? A randomised controlled trial

Objectives:

To compare 10-day and 14-day change regimens to achieve orthodontic tooth movement (OTM) in patients wearing clear aligners and to determine their subsequent pain perception.

Material and methods:

A total of 175 clear aligner patients were assessed for eligibility. Seventy-two patients were randomly assigned to a 10-day group (N = 36) and a 14-day group (N = 36) and were instructed to change the appliances every 10 or 14 days, respectively. OTM efficacy and OTM variation between the actual and predicted OTM digital models measured by shell-to-shell deviation, as well as pain perception determined by a visual analog scale (VAS), were assessed at T0 (baseline, before the placement of the aligners), T1 (stage 8, after completion of aligners #8), and T2 (stage 16, after completion of aligners #16).

Results:

The 10-day and 14-day groups showed similar OTM efficacy at both T1 and T2 for all types of tooth movements (p > 0.09 for all) and similar OTM shell-to-shell deviation at T1 (p = 0.06) and T2 (p = 0.22). The two groups also had similar VAS scores of pain perception throughout the study (p > 0.05 for all).

Conclusion:

The 10-day and 14-day groups showed similar tooth movement and pain perception, suggesting that the clear aligners may be changed every 10 days without a significant compromise in the clinical efficacy of OTM and patient comfort.

Trial registration:

ChiCTR, ChiCTR-IOR-15007532. Registered 17 November 2015, https://www.chictr.org.cn/showproj.aspx?proj=12500

Treatment of class II malocclusion with Invisalign®: A pilot study using digital model-integrated maxillofacial cone beam computed tomography

Background/purpose

The treatment effects of Invisalign® are still obscure due to methodological limitations of previous studies. We introduced a method to comprehensively evaluate the dental and skeletal changes of Class II malocclusion treated non-extraction with Invisalign® and compare with the virtual simulation of ClinCheck® using digital models integrated into maxillofacial cone-beam computed tomography (CBCT).

Materials and methods

The pretreatment (T1) and posttreatment (T2) scanned digital images of actual dentitions were integrated into maxillofacial CBCT images. To evaluate three-dimensional movement of maxillary teeth and change of mandible position, T1 and T2 digital model-integrated maxillofacial CBCT images were superimposed using voxel-based registrations of stable cranial base structures. To evaluate movement of mandibular teeth, model-integrated mandibular CBCT superimposition was registered on mandibular basal bone. To compare achieved and predicted tooth movements, the actual dental images and the virtual digital models created by ClinCheck® were registered on the T1 dentitions.

Results

For simulated upper first molar (U6) distalization of more than 1 mm, treatment accuracy ranged from 31.1% to 40.1%, which was significantly less than virtual planning and previous reports. In unilateral Class II subjects, the amount of U6 distalization on the Class II side was not significantly different from contralateral side, indicating efficacy of sequential distalization was questionable. Those with favorable overjet correction showed evidence of condylar distraction.

Conclusion

Digital model-integrated CBCT superimpositions reflected the actual treatment changes in comparison with the virtual simulation, and showed that ideal occlusion was not achieved in mild to moderate Class II adult patients treated non-extraction with Invisalign®.

Factors affecting the efficacy of Invisalign in anterior tooth rotation

INTRODUCTION

The objectives of this study were to evaluate the clinical efficacy of SmartTrack aligner in rotational movement of the anterior tooth by 15°-30°, and to analyze the factors influencing anterior tooth rotational movement.

METHODS

A total of 212 teeth, including 4 tooth types (maxillary central incisor, maxillary lateral incisor, mandibular central incisor, and mandibular canine) that require anterior tooth rotational movement by 15°-30° were selected from 123 patients, with a mean age of 25.6 years. Rotational movements were calculated from the superimposition of the initial and predicted models (predicted rotational movement) and from the superimposition of the initial and achieved models (achieved rotational movement) using the best-fit alignment tool in NX Imageware. The difference between the predicted and achieved rotational movements (DPARM) was calculated. Univariate analysis, categorical regression analysis, and subgroup analysis were performed on 7 variables: age, gender, tooth type, predicted rotational movement, attachment type, interproximal reduction (IPR), and the total number of active aligners.

RESULTS

The mean DPARM when the anterior tooth was rotated 15°-30° was 4.46° (range, -3.52° to 25.28°). Regression analysis showed that the patient's age, IPR, tooth type, and predicted rotational movement affected DPARM (P <0.01).

CONCLUSIONS

Factors influencing the DPARM of the anterior tooth include the patient's age, tooth type, the magnitude of the predicted rotational movement, and whether or not IPR was prescribed.

What percentage of patients switch from Invisalign to braces? A retrospective study evaluating the conversion rate, number of refinement scans, and length of treatment

INTRODUCTION

This retrospective clinical study aimed to determine what percentage of patients switched from Invisalign to braces to finish treatment. We also examined the number of refinement scans per treatment and the estimated vs actual length of treatment.

METHODS

Records from 500 patients (average age 33.6 years) that started with Invisalign Full or Invisalign Teen were gathered from 2 orthodontic offices and evaluated. Data was collected from the doctors' consultation notes, treatment notes, and Invisalign Web site databases. There were 2 independent variables: gender (male and female) and age groups (aged <20 years, 20-30 years, and >30 years).

RESULTS

One in every 6 patients (17.2%) switched from Invisalign to braces. Invisalign treatment required an average of 2.5 refinement scans, and only 6.0% of patients could complete their treatment without a single refinement scan. The average length of Invisalign treatment was 22.8 months, this was 5.1 months more than the estimated length. The average number of aligners was 64.1, but for the patients that switched to braces, the average number of aligners was 80.6 plus an additional 6.9 months of braces. There was no statistical difference between gender or age group and the conversion to braces. However, patients in the oldest age group had a significantly greater number of refinement scans.

CONCLUSIONS

We are likely overestimating an office's efficiency using Invisalign. On average, an Invisalign patient will require approximately 2-3 refinement scans and 2 years of treatment, and there should be a reasonable expectation that braces may be needed.

Predictability of lower incisor tip using clear aligner therapy

Background

Uprighting incisors is particularly important with clear aligner therapy as incisor tip determines the mesio-distal space needed in the arch, and consequently the fit of the aligner. The objective of this study was to investigate the accuracy of ClinCheck® software to predict lower incisor tip by comparing digitally prescribed movements with actual clinical outcomes and to determine whether the presence of a vertically orientated rectangular composite attachment influences the efficacy of incisor tip.

Methodology

This retrospective study included 66 lower incisors from 42 non-extraction adult patients treated using the Invisalign® appliance. Twenty-one incisors had vertical attachments, while 45 incisors did not have any attachments. Lower incisor tip was measured at T0 (pre-treatment), T1 (predicted post-treatment) and T2 (achieved post-treatment) on digital models using metrology software. The change in position from T0 to T1 and T0 to T2 was measured from the estimated centre of resistance (CRes) of each tooth. The estimated centre of rotation was plotted relative to the CRes to describe the type of orthodontic tooth movement (OTM) predicted and achieved.

Results

Predicted incisor tip and achieved incisor tip were positively correlated (R2 = 0.55; p < 0.001). For every degree of tip planned 0.4 degrees of tip was achieved. The presence of an attachment resulted in 1.2 degrees greater tip (F = 3.7; p = 0.062) and 0.5 mm greater movement of the predicted apex of the tooth (F = 4.3; p = 0.042) compared with the no attachment group. The type of OTM achieved differed from the type predicted. Sixty-seven percent of incisors investigated were predicted to move by root movement, while 46% achieved this type of movement.

Conclusions

The amount of lower incisor tip achieved was on average substantially less than the ClinCheck® displayed. Vertically orientated rectangular attachments are recommended where large root movement is planned, and their presence slightly improves apex movement.

Assessment of malalignment factors related to the Invisalign treatment time aided by automated imaging processes

OBJECTIVES

To identify predictors regarding the type and severity of malocclusion that affect total Invisalign treatment duration based on an intraoral digital scan.

MATERIALS AND METHODS

The subjects of this retrospective clinical cohort were 116 patients treated with Invisalign. A deep learning method was used for automated tooth segmentation and landmark identification of the initial and final digital models. The changes in the six degrees of freedom (DOF), representing types of malalignment, were measured. Linear regression was performed to find the contributing factors associated with treatment time. In addition, the Peer Assessment Rating (PAR) score and a composite score combining 6 DOF were correlated separately to the treatment time.

RESULTS

The number of trays differed between sexes (P = .0015). The absolute maximum torque was marginally associated with the total number of trays (P = .0518), while the rest of the orthodontic tooth movement showed no correlation. The composite score showed a higher correlation with the total number of trays (P = .0045) than did individual tooth movement. Pretreatment upper and lower anterior segment PAR scores were positively associated with the treatment time (P < .001).

CONCLUSIONS

There is not enough evidence to conclude that certain types of tooth movement affect the total aligner treatment time. A composite score seems to be a better predictor for total treatment time than do individual malalignment factors in aligner treatment. Upper and lower anterior malalignment factors have a significant effect on the treatment duration.

Leveling the curve of Spee: Comparison between continuous archwire treatment and Invisalign system: A retrospective study

INTRODUCTION

The purpose of this study was to evaluate and compare leveling of the curve of Spee (COS) achieved by traditional fixed appliances and Invisalign clear aligners (Align Technology, Santa Clara, Calif).

METHODS

This retrospective study involved 2 groups of subjects with an increased COS depth. Patients treated with the Invisalign system (I group) and patients treated with the standard edgewise full-fixed appliance (F group). The I group included 30 subjects (13 males, 17 females; mean age, 24 years 5 months ± 19 months). The F group included 32 subjects (12 males, 20 females; mean age, 22 years 4 months ± 21 months). The 2 groups were matched for sex, age, vertical pattern, and observation period. Pretreatment (T0) and posttreatment (T1) lateral cephalograms were analyzed. COS depth was measured on digital dental casts. The intragroup variation between T0 and T1 was analyzed with a paired t test. The intergroup variation was evaluated using an unpaired t test.

RESULTS

The leveling of COS was statistically significant, comparing T0 and T1 within the groups. The F group presented a statistically significant extrusion of posterior teeth, with a flaring of the mandibular incisors. The I group showed a statistically significant intrusion of the mandibular incisors, with excellent control in the proclination of incisors during the intrusion movement.

CONCLUSIONS

Traditional continuous archwire treatment and the Invisalign system effectively level the COS.

Presurgical orthodontic decompensation with clear aligners

INTRODUCTION

Orthodontists, surgeons, and patients have taken an interest in using clear aligners in combination with orthognathic surgery. This study aimed to evaluate the accuracy of tooth movements with clear aligners during presurgical orthodontics using novel 3-dimensional superimposition techniques.

METHODS

The study sample consisted of 20 patients who have completed presurgical orthodontics using Invisalign clear aligners. Initial (pretreatment) digital dental models, presurgical digital dental models, and ClinCheck prediction models were obtained. Presurgical models were superimposed onto initial ones using stable anatomic landmarks; ClinCheck models were superimposed onto presurgical models using surface best-fit superimposition. Five hundred forty-five teeth were measured for 3 angular movements (buccolingual torque, mesiodistal tip, and rotation) and 4 linear movements (buccolingual, mesiodistal, vertical, and total scalar displacement). The predicted tooth movement was compared with the achieved amount for each movement and tooth, using both percentage accuracy and numerical difference.

RESULTS

Average percentage accuracy (63.4% ± 11.5%) was higher than in previously reported literature. The most accurate tooth movements were buccal torque and mesial displacement compared with lingual torque and distal displacement, particularly for mandibular posterior teeth. Clinically significant inaccuracies were found for the buccal displacement of maxillary second molars, lingual displacement of all molars, intrusion of mandibular second molars, the distal tip of molars, second premolars, and mandibular first premolars, buccal torque of maxillary central and lateral incisors, and lingual torque of premolars and molars.

CONCLUSIONS

Superimposition techniques used in this study lay the groundwork for future studies to analyze advanced clear aligner patients. Invisalign is a treatment modality that can be considered for presurgical orthodontics-tooth movements involved in arch leveling and decompensation are highly accurate when comparing the simulated and the clinically achieved movements.

Assessment of orthodontic treatment efficacy of Clarity Aligners using the Peer Assessment Rating index and the American Board of Orthodontics Cast-Radiograph Evaluation

INTRODUCTION

3M Oral Care Solutions (St Paul, Minn) has recently introduced Clarity Aligners into the market. This cohort study evaluated the orthodontic treatment efficacy of this clear aligner system using the Peer Assessment Rating (PAR) index and the American Board of Orthodontics Cast-Radiograph Evaluation (CR-Eval).

METHODS

Pretreatment and posttreatment dental models of 87 subjects who had undergone orthodontic treatment using Clarity Aligners in both arches to align their teeth to a target setup were independently evaluated by 4 examiners using the PAR index and the American Board of Orthodontics CR-Eval. Changes in CR-Eval and PAR scores from pretreatment to posttreatment were calculated, with PAR score reductions also expressed as percentages.

RESULTS

Treatment with Clarity Aligners reduced the CR-Eval scores from 39.05 ± 14.98 to 30.34 ± 8.76, resulting in a statistically significant difference of 8.76 ± 11.45 between pretreatment and posttreatment scores. Similarly, aligner treatment reduced the weighted PAR scores from 13.40 ± 9.26 to 5.80 ± 4.84, resulting in a statistically significant difference of 7.50 ± 7.56 between pretreatment and posttreatment scores. The overall median PAR reduction was 53%, with 94% of the subjects having reduced PAR scores after treatment. Seventy-eight percent of subjects had >30% PAR reduction, 57% had >50% PAR reduction, and 33% had >70% PAR reduction.

CONCLUSIONS

The results suggest that Clarity Aligners may be an effective treatment modality in mild to moderate malocclusions.

Efficacy of Anterior Tooth Simulations with Clear Aligner Therapy - A Retrospective Cohort study of Invisalign and Flash Aligner Systems

Purpose:

The purpose of this study was to compare the efficacy of tooth movement between two clear aligner systems by comparing the predicted treatment outcomes versus actual outcomes achieved using a 3D best-fit algorithm.

Materials & Methods:

Clear aligner therapy (CAT) was used to treat 62 patients; n=38 Invisalign® and n=24 Flash®. The Invisalign group had a male to female distribution of 13:25 and a mean age of 35.5, while the Flash group had a male to female distribution of 6:18, with a mean age of 29.2. Differences in predicted versus achieved actual outcomes were compared using eModel Compare 8.1 software.

Results:

1) Intra-group differences between predicted and achieved tooth movements for angular movements were statistically (P<0.05) and clinically (>2°) significant with both treatment methods, except for tipping of maxillary and mandibular incisors for Flash® (<2◦). 2) Inter-group results demonstrated statistically significant differences in favor of Flash® for maxillary central incisor Tip (1.3°), BL movements for maxillary canines (0.1mm), and mandibular central incisor Rotations (1°). These did not exceed the threshold for the clinical relevance of 2° or 0.5mm.

Conclusions:

There were no differences in clinical accuracy and efficacy between Invisalign or Flash aligner systems in achieving predicted tooth movement.

Association between initial complexity, frequency of refinements, treatment duration, and outcome in Invisalign orthodontic treatment

INTRODUCTION

This study explored possible associations between treatment duration, initial complexity, outcomes in Invisalign therapy, and the number of refinements.

METHODS

Three-dimensional models (initial, final, and refinements) of 355 Invisalign patients (114 males and 241 females; 33.8 ± 17.1 years) were analyzed using the Peer Assessment Rating (PAR) index questionnaire tool in the Ortho Analyzer software (version 2.0; 3Shape, Copenhagen, Denmark) to calculate the weighted total and individual PAR index scores for each component of the PAR index. Data related to demographics, treatment duration, and the number of refinements were collected.

RESULTS

Treatment duration increased as the number of refinements increased. Percent of improvement was higher in PAR ≥22 group than PAR <22 with an increase in the number of refinements: 83.3% vs 73.8% for 2 refinements; 94.7% vs 91.2% for 3 refinements; and 100% vs 85.7% for ≥4 refinements. Those who achieved great improvement or improvement and those who did not were significantly different in treatment duration (P <0.001 and P = 0.027), number of refinements (≥3 refinements; P <0.001), initial occlusal severity (PAR ≥22; P <0.01 and P = 0.031). Most subjects achieved improvement after the first refinement (64.5% for PAR <22 and 78.5% for PAR ≥22). Few had ≥4 refinements, and if they did, none achieved improvement with additional refinements.

CONCLUSIONS

Initial complexity for an Invisalign case is associated with treatment duration, achieved outcomes, and the number of refinements. Treatment duration increased with an increased number of refinements. Great improvement or improvement for the first time dropped to 0 if additional refinements were carried out after 3. Therefore, performing additional refinements does not necessarily mean better occlusal outcomes.

Clinical expression of programmed mandibular canine rotation using various attachment protocols and 1- vs 2-week wear protocols with Invisalign SmartTrack aligners: A retrospective cohort study

INTRODUCTION

Rotation of rounded teeth, particularly canines, is reported as one of the most difficult and inaccurate tooth movements with aligners. This retrospective study aimed to assess the accuracy and reliability of prescribed mandibular canine rotation with Invisalign aligners and the influence of attachment type and wear schedule on accuracy.

METHODS

A sample of 75 subjects with mandibular canines requiring rotation was collected from an existing database. The initial, predicted finish, and achieved finish, were measured using metrology software, and the differences between predicted and achieved mandibular canine rotations were calculated. The sample was divided into 3 groups: optimized rotation attachments using 1-week wear, optimized rotation attachments using 2-week wear, and conventional rectangular attachments using 2-week wear.

RESULTS

Rotation was an underexpressed movement, with an overall median sample efficiency of 75.4%. For all groups, predicted rotation was not equivalent to achieved rotation at a ± 5° equivalence margin. This indicates that none of the Invisalign SmartTrack aligner attachment configurations display clinical accuracy in their predicted rotation. By attachment type, median efficiencies of 81.5%, 76.5%, and 63.1% were found for groups 1-week wear, 2-week wear, and 2-week wear, respectively. By wear schedule, there was no significant difference in efficiency for optimized rotation attachments.

CONCLUSIONS

The clinical expression of canine rotation with SmartTrack aligners is less than the prescribed rotation for all attachment configurations. Vertical rectangular attachments were associated with the least accurate expression of prescribed movement. There was no difference in rotation efficiency between 1- or 2-week aligner wear.

Predictability of overbite control with the Invisalign appliance comparing SmartTrack with precision bite ramps to EX30

INTRODUCTION

Although the Invisalign appliance has reported difficulty in achieving the overbite outcomes predicted by ClinCheck software (Align Technology, Santa Clara, Calif), the effect of modifications to the material and components of the appliance are largely unquantified. This study aimed to investigate and determine the accuracy of Invisalign in correcting a deep overbite by comparing the predicted outcome from ClinCheck to the achieved posttreatment outcome for treatment groups that use different components of the appliance system.

METHODS

A retrospective study was conducted using pretreatment and posttreatment intraoral scans and predicted outcomes (ClinCheck) stereolithography files of 2 groups of consecutively treated adult patients from private specialist orthodontic practices, 1 group treated with EX30 material with no bite ramps (n = 29) and 1 treated with the newer SmartTrack material and precision bite ramps (n = 39). Inclusion criteria comprised nonextraction treatment, with a minimum of 14 dual arch Invisalign aligners using a 2-weekly aligner change protocol. Geomagic Control X software (3D Systems, Rock Hill, SC) was used to measure overbite in the pretreatment, posttreatment, and predicted outcome stereolithography files for each patient. Results were compared with a previously published treatment group that used SmartTrack material and no precision bite ramps.

RESULTS

The regression coefficient analysis indicated that for both groups, the deeper the pretreatment overbite and the greater overbite reduction projected according to ClinCheck, there is a linear increase in the discrepancy of overbite expression posttreatment. ClinCheck overpredicted overbite reduction in 96.6% of patients with precision bite ramp in which, on average, 43.4% of the prescribed overbite reduction was expressed. For EX30 patients, ClinCheck overpredicted overbite reduction in 87.2% of patients in which, on average, 55.1% of the prescribed overbite reduction was expressed.

CONCLUSIONS

The use of precision bite ramps does not appear to significantly improve the ability of SmartTrack material to predictably open the bite. SmartTrack material with or without bite ramps does not appear to produce better bite opening predictability than that seen with EX30 material.

Comparison of clinical outcomes between Invisalign and conventional fixed appliance therapies in adult patients with severe deep overbite treated with nonextraction

INTRODUCTION

The use of aligner therapy for orthodontic treatment has increased substantially in the past decade. However, no study has compared treatment outcomes between the conventional fixed appliance and Invisalign therapies in patients with a severe deep overbite.

METHODS

This study included 50 consecutive adult patients who underwent treatment with either Invisalign (n = 25; mean age, 23.3 ± 8.5 years) or a conventional fixed appliance (n = 25; mean age, 23.1 ± 6.5 years) to correct overbite >5 mm and >60% deep overbite. Cephalometric analysis and peer assessment rating was used to compare the clinical outcome between groups.

RESULTS

Cephalometric analysis showed significant differences in N-Me (P = 0.0005) and Mp-L6 (P = 0.0001) between Invisalign and fixed appliance treatment groups. No significant differences were observed in the peer assessment rating analysis or total treatment duration between the 2 groups.

CONCLUSIONS

Both Invisalign and conventional fixed appliances were effective in treating patients with a severe deep overbite. Invisalign therapy may be preferable over conventional fixed appliance therapy in patients with high angle and deep overbite. However, because this study had a retrospective design, the results should be viewed with caution.

Digital model superimpositions: are different software algorithms equally accurate in quantifying linear tooth movements?

Background

To evaluate the accuracy of three different 3D digital model registration software packages for linear tooth movement measurements, with reference to a 3D digital virtual setup (DS).

Methods

Twenty maxillary and mandibular pre-treatment scans of patients undergoing clear aligner therapy were used. Digital Setups were generated from pre-treatment scans using OrthoAnalyzer software. Both the pretreatment digital scans (T1) and Digital Setups (T2) were converted to STL files to be imported to the three studied software packages: Geomagic, OrthoAnalyzer and Compare. Linear changes in tooth positions were calculated for all the registered pairs.

Results

The change in tooth position was compared between the calculated tooth movement using each of the registration software packages versus the actual generated tooth movement from the Digital Setups. Continuous data was expressed as mean and standard deviation. Intraclass Correlation Coefficients for agreements between Digital Simulation and each software was used. Intra and Inter-examiner reliabilities were also assessed using Intraclass Correlation Coefficients. Significance of the obtained results was expressed at p ≤ 0.01. Geomagic software showed agreements > 0.90 for maxillary linear tooth movements and between 0.75 and 0.90 for mandibular measurements. OrthoAnalyzer software showed agreements between 0.50 and < 0.75 for maxillary and mandibular measurements. Compare software showed agreements > 0.90 for maxillary and mandibular linear tooth movements, indicating the best consistency.

Conclusions

Compare and Geomagic software packages consistently showed maximum accuracy in measuring the amount of tooth movement in the maxillary arch compared to the reference standard. Compare software showed the highest agreements in the mandibular arch. None of the three studied software packages showed poor agreement with the Digital Setup across all tooth movement measurements. Buccolingual tooth movements showed the highest agreements amongst linear measurements.

Remote digital monitoring during the retention phase of orthodontic treatment: A prospective feasibility study

Objective

To evaluate if a remote digital monitoring system added at the end of orthodontic treatment could positively influence the retention phase by reducing the occurrence of misfit of removable appliances, number of emergency appointments (EA), and orthodontic relapse.

Methods

Twenty-seven patients who completed active orthodontic treatment were divided into the study and control groups. In addition to the standard chairside follow-up appointments at month 1 (T1), month 3 (T2), month 6 (T3), the study group patients were monitored using Dental Monitoring® with monthly intra-oral scans. Occurrence of misfit of removable retainers, number of EAs, and intercanine width change were recorded for both groups. Differences in EAs and retainer fit were assessed using the chi-square test. Intra-group and inter-group differences in the intercanine width were assessed with Friedman test and Mann-Whitney U test, respectively (α = 0.05).

Results

The study group showed a significantly lower occurrence of misfit of removable retainers (p = 0.027) compared to the control group. No significant inter- and intra-group difference was found in the EAs and intercanine width change at each time-point.

Conclusions

Integrating remote monitoring systems, such as Dental Monitoring®, to the retention phase of the orthodontic treatment may lower the occurrence of misfit of removable retainers. However, a small sample size and a short observation period limit the strength of this evidence. These preliminary results tentatively suggest that remote monitoring technologies may be beneficial, especially during the COVID-19 pandemic, when the regularity of in-office visits might be disrupted.

Accuracy of dental arch form in customized fixed labial orthodontic appliances

INTRODUCTION

This study evaluated arch form accuracy with or without premolar extraction in customized fixed labial orthodontic appliance treatment.

METHODS

Setup and posttreatment digital models of 27 samples (15 extractions and 12 nonextractions) were selected and superimposed by best-fit surface-based registration in both the maxilla and the mandible. The facial axis points were identified and converted into Cartesian coordinates. A sixth-order polynomial equation was used to fit dental arches. Arch discrepancies (the mean distance between 2 arch forms) and similarities were compared between extraction and nonextraction groups, maxilla and mandible, and anterior and posterior arches.

RESULTS

The arch discrepancy between extraction and nonextraction groups showed no statistically significant difference, but a statistically significant difference in arch similarity was found in the mandible. There were statistically significant differences between anterior and posterior arch discrepancies in the extraction (mandible) and the nonextraction (maxilla and mandible) groups. However, no statistically significant correlation was shown between anterior and posterior arch discrepancies. The arch similarities were 96.18% and 97.38% in the maxilla and 96.01% and 97.49% in the mandible between extraction and nonextraction groups. Arch form discrepancies and similarities showed a moderate correlation but no statistically significant differences between the maxilla and the mandible.

CONCLUSIONS

In customized fixed labial orthodontic appliance treatment, arch form setup can be accurately achieved with and without premolar extraction. Anterior arch form acquires fewer discrepancies than the posterior arch, and overcorrection should be added to the end of the customized archwire to reduce posterior arch discrepancies. The discrepancy of the maxillary and mandibular arches is interrelated, and adjustments should be made on both maxillary and mandibular archwires to correct single-jaw transverse malposition.

TIP, TORQUE & ROTATIONS: How accurately do digital superimposition software packages quantify tooth movement?

Background

To investigate the accuracy of three different 3D digital model registration software for tip, torque and rotation measurements, with reference to a 3D digital virtual setup. Twenty maxillary and mandibular pre-treatment scans of patients undergoing clear aligner therapy were used. Digital setups were generated from pre-treatment scans using a tooth movement software. Both the pretreatment digital scans (T1) and digital setups (T2) were converted to STL files to be exported to the 3 studied software that employed: (1) Semiautomatic best fit registration (S-BF), (2) Interactive surface-based registration (I-SB), and (3) Automatic best fit registration (A-BF) respectively. Changes in tip, torque and rotation were calculated for all the registered pairs.

Results

The change in tooth position was compared between the calculated tooth movement using each of the registration software packages versus the actual generated tooth movement from the digital setups. Continuous data was expressed as mean and standard deviation. Intra Class Correlation Coefficient for agreement between digital simulation and each software was used. Intra and Inter-examiner reliabilities were also assessed using Intra Class Correlation Coefficient. Significance of the obtained results was expressed at p ≤ 0.01. Semiautomatic best fit registration software showed excellent agreement (> 0.90) for all tooth movements, except for good agreement for torque (0.808). Interactive surface-based registration software showed moderate agreement for all measurements (0.50 and < 0.75), except for good agreement for rotation (0.783). Automatic best fit registration software demonstrated excellent agreement (> 0.90) for rotation, good agreement for tip (0.890) and moderate agreement for torque (0.740).

Conclusions

Overall, semiautomatic best fit registration software consistently showed excellent agreement in superimpositions compared to other software types. Automatic best fit registration software consistently demonstrated better agreement for mandibular superimpositions, compared to others. Accuracy of digital model superimpositions for tooth movements studied in superimposition studies, can be attributed to the algorithm employed for quantification.

Evaluation of interproximal reduction in individual teeth, and full arch assessment in clear aligner therapy: digital planning versus 3D model analysis after reduction

Aim

To evaluate the correspondence between the interproximal reduction (IPR) performed clinically and that programmed in ClinCheck® and further assess which teeth showed an amount of implemented IPR (I-IPR) that corresponds with that programmed in ClinCheck®.

Materials and methods

Pre- (T0) and post-treatment (T1) ClinCheck® digital models for 75 subjects (30 males and 45 females), mean age (38 ± 15) years, were included. To calculate the amount of I-IPR, Ortho Analyzer software (3Shape, Copenhagen, Denmark) was used to measure the mesiodistal widths for the maxillary and mandibular teeth from second premolar to the contralateral second premolar on the initial (T0) and final (T1) STL models. I- IPR performed by tooth was obtained by comparing the mesiodistal width of each tooth at T0 and T1. The amount of programmed IPR (P-IPR) in ClinCheck® was compared to that implemented clinically using the following formula: IPR difference = (P-IPR) − (I-IPR).

Results

Statistically significant differences were observed between the average value of digitally programmed and implemented IPR per tooth for both the maxillary (p < .0001) and mandibular (p < .0001) teeth. The mean P-IPR for the maxillary teeth was 0.28 ± 0.16 mm versus the mean I-IPR of 0.15 ± 0.15 mm. In the mandibular arch, the mean P-IPR was 0.31 ± 0.17 mm, while the I-IPR was 0.17 ± 0.16 mm. The mean I-IPR was consistently lower than the mean P-IPR regardless of teeth and sites (p < 0.0001). The difference between the P-IPR compared to the I-IPR was larger for mandibular anterior teeth than for maxillary anterior teeth (p = 0.0302) and larger for maxillary posterior teeth than mandibular posterior teeth (p = 0.0059).

Conclusion

The amount of implemented-IPR in clear aligner therapy is less than that digitally programmed for most teeth. Regardless of the regions, I-IPR was consistently lower than that programmed. Mandibular anterior teeth and maxillary posterior teeth showed greater discrepancy between P-IPR and I-IPR than the maxillary anterior and mandibular posteriors. Further prospective studies are needed to determine the factors affecting the precision of IPR and the clinical implications of a significantly reduced I-IPR on treatment outcomes.

Adaptational changes in clear aligner fit with time

OBJECTIVES

To analyze adaptational changes in clear aligner fit after intraoral usage at different sets of time.

MATERIALS AND METHODS

Eight Invisalign appliances (Align Technology, San Jose, California, USA) were collected after intraoral usage. Acrylic imprints of the lower incisor region were constructed for each appliance at T0 (unused appliance). Two appliances were then used intra-orally for each of the following defined periods of time: 3 days, 7 days, 10 days, or 15 days. Used aligners were adapted on its T0 imprint and both were sectioned buccolingually from the distal surfaces of each incisor at the attachment area. Eight surfaces were collected for each set of time (n = 32 surfaces). Microphotographs of obtained sections and micrometric measurements of aligner fit were recorded at five different levels using scanning electron microscopy (SEM). Mean values of the fit changes (gap width) and group comparisons were statistically analyzed using analysis of variance and Tukey's post hoc tests. Significance level was set at P < .05.

RESULTS

Highly significant differences in aligner fit were found at the different time points assessed (P < .001) with the least mean gap width at 15 days (176 ± 98 μm) and the highest at 7 days (269 ± 145 μm). Significant differences in aligner fit at different attachment levels were also found (P < .01) with the least mean gap width at the middle of the labial surface of the attachment (187 ± 118 μm).

CONCLUSIONS

The 15-day period of intraoral aligner wear might still be recommended as it showed the best adaptation and least gap width between the aligner and the attachment.

Consistency and Reliability Analyses of a Comprehensive Index for the Evaluation of Teeth Alignment Performance

(1) Introduction: The purpose of this work was to describe a method and propose a novel accuracy index to assess orthodontic alignment performance. (2) Methods: Fifteen patients who underwent orthodontic treatment using directly printed clear aligners were recruited. The study sample included 12 maxillary and 10 mandibular arches, whose pre-treatment, predicted and post-treatment digital models were superimposed on the untreated posterior teeth by means of a best-fit surface-based registration, which was also used to transfer three anatomical landmarks, digitally labeled on the crown of each anterior moving tooth, from the pre-treatment to the predicted and post-treatment models. The Teeth Alignment Performance (TAP) index, quantifying how close the final landmarks were to their expected final position, was proposed as an accuracy index of both individual tooth and group of teeth movement, and its inter-examiner repeatability was tested. (3) Results: No systematic inter-rater discrepancy associated with TAP was observed (p > 0.05), not even when a slight systematic inter-rater difference in landmark labelling was detected (for the upper central incisors, p < 0.001). In addition, all Intra-class Correlation Coefficient (ICC) values showed excellent inter-rater agreement (>0.95), and the small Random Error of Measurement (REM), ranging from 1% for the arch TAP to 3% for the lower canine TAP, indicated that this accuracy index is highly repeatable. (4) Conclusions: The TAP index was proven to be comprehensive, consistent and reliable in assessing the performance of teeth alignment according to a digital plan. The proposed method is also suitable to be implemented in the clinical digital workflow.

Performance of Rigid and Soft Transfer Templates Using Viscous and Fluid Resin-Based Composites in the Attachment Bonding Process of Clear Aligners

Objectives

The study aims at assessing the accuracy of the process of attachment bonding in aligner treatments. The analysis leads to the error estimation in the faithful reproduction of master model attachments using two types of transfer templates and two light-curing resin-based composites usually used in orthodontics.

Methods

The authors have used two transfer templates made of two different materials. The first, named Leone-biocompatible thermoforming material hard/soft, has a lower Young's modulus and is labelled as soft, while the other, named Leone-biocompatible thermoforming material, is marked as rigid. The resin-based composites possess different mechanical and rheological properties. Specifically, Transbond™ XT Light Cure Paste Adhesive, 3M has a higher viscosity than the TetricEvoflow, Ivoclar Vivadent, a flowable nanohybrid composite. The authors attempt to estimate the performance ranking between the four possible couples obtained by combining the two light-curing resin-based composites and transfer templates. Each combination was repeated in six models and compared with twelve master models, resulting in 36 total samples. A 3-D laser scanner is used to generate a digital model of each model. The comparison between digital models is the base for a comparative assessment in terms of relative and absolute error. The relative error is estimated using scalar performance indicators ranging from 0 to 1, where 1 indicates the optimum matching. The absolute error estimated from the mean square error between the coordinates of each digital model yields the reproduction accuracy in micrometer. Furthermore, the authors attempted to assess the error distribution by evaluating the point-by-point difference between the digital models.

Results

This analysis aims at localizing the sources of error in the considered models. The use of Transbond™ XT Light Cure Paste Adhesive, 3M with a rigid transfer template is always associated with significant accuracy and minor dispersion. However, in a few instances, using the soft template or the flowable resin-based composite can lead to bad performances. Significance. The data processing bestowed the following performance ranking from the first with lower reproduction error to the last characterized by the worst performance: (1) attachments bonding with rigid template and Transbond™ XT Light Cure Paste Adhesive, 3M, (2) attachments bonding with soft template and Transbond™ XT Light Cure Paste Adhesive, 3M, (3) attachments bonding with rigid template and TetricEvoflow, Ivoclar Vivadent, and (4) attachments bonding with soft template and TetricEvoflow, Ivoclar Vivadent.

Accuracy of Tooth Movement with In-House Clear Aligners

AIM

To evaluate accuracy of tooth movements with in-house clear aligners.

METHODS

This prospective clinical study included 30 participants for anterior clear aligners with crowding not exceeding 4 mm. per arch, non-extraction cases with no changes in posterior relationship. Aligners were created with OrthoAnalyzer^TM software, attachments were placed as needed and IPR was performed in required areas. The final stage of tooth movement was compared with predicted tooth movement by superimposition of the two STL models. Maxillary arch was superimposed on stable posterior teeth and best fit on palatal rugae while mandibular arch was superimposed on unmoved posterior teeth. The amount of differences in predicted and achieved tooth movements were compared. Six types of tooth movement were included in the comparison which were labial, lingual, mesiodistal, intrusion, extrusion and rotation.

RESULTS

Total sample consisted of 259 anterior teeth (126 maxillary, 133 mandibular). The achieved tooth movements were significantly lesser than the predicted tooth movements in all the six types of tooth movement. Overall accuracy of tooth movement with clear aligner was 56.18%. The most accurate tooth movement was mesiodistal (72.33%). The least accurate movement was intrusion (43.28%). While mesiodistal, labial, rotation and lingual tooth movements were more predictable than intrusion and extrusion.

CONCLUSION

Understanding the accuracy of different tooth movements might help in case selection, treatment plan and development or increase accuracy and predictability of in-house clear aligners.

Clinical expression of programmed rotation and uprighting of bilateral winged maxillary central incisors with the Invisalign appliance: A retrospective study

INTRODUCTION

Winged maxillary central incisors (WMCI), defined as mesiopalatal rotation of the crowns of maxillary central incisors, is a common dental trait that affects smile esthetics. This retrospective study aimed to determine the efficacy of rotation and uprighting tooth movements of bilateral WMCI with Invisalign (Align Technology, Santa Clara, Calif).

METHODS

Initial, predicted, and achieved stereolithography files of 30 adult patients, consecutively treated with the Invisalign SmartTrack appliance, were superimposed using Geomagic Control X 64 (3D Systems, Rock Hill, SC). The pairs of incisors were assessed for rotation using the interlabial angle (ILA), and individual incisors were measured for rotation and tip.

RESULTS

Programmed rotation and uprighting of WMCI are mostly undercorrected with the Invisalign appliance. The mean shortfall in ILA was 10.5° (standard deviation [SD], 10.66; 95% confidence interval [CI], 5.89-14.19; P <0.001) for a mean predicted change of 35.27°. For individual incisors, a mean shortfall of 5.38° (SD, 5.88; 95% CI, 3.58-6.76; P <0.001) was found for a mean 18.75° predicted change in rotation. A mean predicted change in tip of 7.06° showed a mean shortfall of was 2.16° (SD, 3.86°; 95% CI, 1.03-3.01; P <0.001). A moderate and statistically significant correlation between shortfalls in rotation and tip was observed (r = 0.44). Linear regression analysis was used to formulate an equation as a clinical tool to determine the likely achieved outcome on the basis of the predicted change.

CONCLUSIONS

Predicted changes in rotation, ILA, and tip were both under and overexpressed. In particular, tip was dependent on the magnitude of planned change. The random inconsistencies in the clinical expression of rotation and tipping warrant careful monitoring and/or remedial actions such as overcorrections aligners.

Predictability of rotational tooth movement with orthodontic aligners comparing software-based and achieved data: A systematic review and meta-analysis of observational studies

OBJECTIVE

To evaluate all available evidence on the prediction of rotational tooth movements with aligners.

DATA SOURCES

Seven databases of published and unpublished literature were searched up to 4 August 2020 for eligible studies.

DATA SELECTION

Studies were deemed eligible if they included evaluation of rotational tooth movement with any type of aligner, through the comparison of software-based and actually achieved data after patient treatment.

DATA EXTRACTION AND DATA SYNTHESIS

Data extraction was done independently and in duplicate and risk of bias assessment was performed with the use of the QUADAS-2 tool. Random effects meta-analyses with effect sizes and their 95% confidence intervals (CIs) were performed and the quality of the evidence was assessed through GRADE.

RESULTS

Seven articles were included in the qualitative synthesis, of which three contributed to meta-analyses. Overall results revealed a non-accurate prediction of the outcome for the software-based data, irrespective of the use of attachments or interproximal enamel reduction (IPR). Maxillary canines demonstrated the lowest percentage accuracy for rotational tooth movement (three studies: effect size = 47.9%; 95% CI = 27.2-69.5; P < 0.001), although high levels of heterogeneity were identified (I2: 86.9%; P < 0.001). Contrary, mandibular incisors presented the highest percentage accuracy for predicted rotational movement (two studies: effect size = 70.7%; 95% CI = 58.9-82.5; P < 0.001; I2: 0.0%; P = 0.48). Risk of bias was unclear to low overall, while quality of the evidence ranged from low to moderate.

CONCLUSION

Allowing for all identified caveats, prediction of rotational tooth movements with aligner treatment does not appear accurate, especially for canines. Careful selection of patients and malocclusions for aligner treatment decisions remain challenging.

Predictability of overbite control with the Invisalign appliance

INTRODUCTION

Control of overbite is considered essential in achieving ideal orthodontic outcomes. Questions have been raised regarding the accuracy of ClinCheck software (Align Technology, Santa Clara, Calif) in predicting posttreatment outcomes with Invisalign, with the paucity of well-researched literature available on this topic. This research aimed to investigate and determine the accuracy of Invisalign (Align Technology) in correcting a deep overbite by comparing the outcomes predicted by ClinCheck with achieved posttreatment outcomes.

METHODS

A retrospective study was conducted using pretreatment and posttreatment intraoral scans and predicted outcome (ClinCheck) stereolithography files of 42 adult patients consecutively treated with Invisalign from January 2014 and completed before July 2018, selected from the files of 1 experienced orthodontist. Patients included in the study were treated without extractions and with a minimum of 14 dual arch Invisalign aligners using a 2-weekly aligner change protocol. The pretreatment, posttreatment, and predicted outcome stereolithography files for each patient were imported into Geomagic Control X (3D Systems, Rock Hill, SC) software to measure overbite.

RESULTS

The deeper the patient's initial overbite and the greater the amount of programmed reduction in overbite according to ClinCheck, the greater the discrepancy in overbite expression posttreatment. ClinCheck over-predicted overbite reduction in 95.3% of patients in which, on average, only 39.2% of the prescribed overbite reduction was expressed.

CONCLUSIONS

Overbite reduction may result in suboptimal outcomes when using the Invisalign appliance unless remedial measures are employed. The deeper the initial overbite, the more challenging it is to achieve the prescribed posttreatment overbite.

Comparison of achieved and predicted crown movement in adults after 4 first premolar extraction treatment with Invisalign

INTRODUCTION

In this study, we compared achieved and predicted crown movements of maxillary and mandibular first molars, canines, and central incisors in adults after 4 first premolar extraction treatment with Invisalign.

METHODS

Seventeen adult patients who received 4 first premolar extraction treatment with Invisalign and completed the first series of aligners were included. Superimposition of pretreatment and actual posttreatment dental models was acquired using registrations of pretreatment and posttreatment craniofacial models on the basis of bone surfaces and registrations of craniofacial and dental models on the basis of dental crown surfaces, respectively. Superimposition of pretreatment and predicted posttreatment models was acquired from ClinCheck software. Achieved and predicted 3-dimensional crown movements of maxillary and mandibular first molars, canines, and central incisors were then compared using the paired t test.

RESULTS

Relative to predicted changes, first molars achieved greater mesial displacement, mesial tipping, and buccal inclination in both the maxilla and mandible, greater intrusion in the maxilla, and greater mesial-lingual rotation and less constriction in the mandible. Canines achieved greater distal tipping in both the maxilla and mandible, less retraction in the maxilla, and greater lingual inclination and extrusion in the mandible. Central incisors achieved greater distal tipping and lingual inclination and extrusion in both the maxilla and mandible and less retraction in the maxilla.

CONCLUSIONS

Tooth crown movements were not fully achieved as predicted following Invisalign treatment. Differences focused on mesial tipping, buccal inclination, mesial displacement, and intrusion of the first molars, as well as distal tipping, lingual inclination, insufficient retraction, and intrusion of the canines and central incisors.

Efficacy and predictability of maxillary and mandibular expansion with the Invisalign® system

Background

The purpose of this study is to evaluate the efficacy and predictability of upper and lower orthodontic expansion with the Invisalign® system.

Material and Methods

From a sample of 167 patients; 64 upper and 51 lower arches were randomly selected from patients who had been treated with plastic orthodontics (Invisalign® aligners, SmartTrack® material). Digital models were extracted at the beginning (ModT1) and at the end of treatment (ModT2) as well as the final ClinCheck® (CkT2). The canine, premolar and molar width was measured at the gingival and cuspid level of both arches, as well as the inclination of the upper first molar. Likewise, both arches were divided regarding the planned expansion at the level of the first molar into mild, moderate and severe.

Results

The efficacy of expansion in the upper and lower arches showed a statistically significant difference (p<0.00005). During the measurements of predictability, around 98-100% was achieved at the coronal level and between 85-90% at the gingival level. Analyzing predictability regarding to the magnitude of expansion, superior and inferior moderate expansion, both gingival and cuspid, presented higher values.

Conclusions

The Invisalign® system aligners (SmartTrack® material), proved to be a positive alternative for expansion movement offering high degree of predictability, both in the upper and lower arches. As a result, the most predictable level of expansion was moderate, having being the lower arch more foreseeable at the gingival level than the upper arch.

Key words:Predictability, Efficacy, Expansion, Aligner, Invisalign®.

Micro computed tomography evaluation of Invisalign aligner thickness homogeneity

OBJECTIVES

To measure the thickness homogeneity of Invisalign (Align Technology Inc, San José, Calif) aligners with micro-computed tomography (micro-CT) scans.

MATERIALS AND METHODS

Starting from micro-CT scanning of 20 different aligners, multiplanar reconstructions were obtained. An orthodontist blinded about the study measured aligner thickness in different regions (molar, canine, incisor) and in different sites (gingival-buccal, buccal, occlusal, lingual, and gingival-lingual). To assess various thicknesses in different aligner sites and regions, the sample was stratified into subgroups and linear regression analysis was performed.

RESULTS

Descriptive analysis showed that mean thickness of aligners in the incisor region ranged from 0.582 mm to 0.639 mm, in the canine region from 0.569 mm to 0.644 mm, and in the molar region from 0.566 mm to 0.634 mm. Student's t-tests showed no significant differences in the aligner thickness of different regions when data were stratified by different sites. Student's t-tests showed significant differences in thickness homogeneity for the molar region when the data were stratified by tooth (mean difference = 0.068 mm; 95% confidence interval, 0.009-0.126 mm; P = .024).

CONCLUSIONS

Invisalign aligner thickness is characterized by small differences. The only significant difference was revealed in the molar region where thickness of the gingival-lingual edge is significantly thinner than that measured at the occlusal aspect. From a clinical perspective, the results of the present study could be considered to explain the reduced predictability of several orthodontic tooth movements in the molar region.

Biomechanical Effects of Torquing on Upper Central Incisor with Thermoplastic Aligner: A Comparative Three-Dimensional Finite Element Study with and Without Auxillaries

Background and Objectives:

This study was conducted to determine the effective method to torque the incisor with thermoplastic aligner using a three-dimensional (3D) finite element method.

Materials and Methods:

Three finite element models of maxilla and maxillary dentition were developed. In the first model, thermoplastic aligner without any auxiliaries was used. In the second and third models, thermoplastic aligner with horizontal ellipsoid composite attachment and power ridge were used, respectively. The software used for the study was ANSYS 14.5 FE. A force of 100 g was applied to torque the upper right central incisor. The resultant force transfer, stress distribution, and tooth displacement were evaluated.

Results:

The overall tooth displacement and stress distribution appeared high in the model with power ridge, whereas the root movement was more in the horizontal ellipsoid composite attachment model. The model without any auxillaries produced least root movement and stress distribution.

Conclusion:

Horizontal ellipsoid composite attachment achieved better torque of central incisor than the model with power ridge and model without any auxillaries.

Effect of clear aligner wear protocol on the efficacy of tooth movement

OBJECTIVES

To compare the efficacy of orthodontic tooth movement with three aligner wear protocols: 7 day, 10 day, and 14 day.

MATERIALS AND METHODS

Eighty patients were randomly allocated into three groups: group A (7-day changes), group B (10-day changes), and group C (14-day changes). The posttreatment scans were compared with the final virtual treatment simulations through digital superimposition. The differences between predicted and actual achieved treatment outcomes were computed in six angular and six linear dimensions. Differences >0.5 mm for linear measurements and >2° for angular measurements were considered clinically relevant.

RESULTS

Within groups, and irrespective of wear protocol, all linear discrepancies in both jaws were deemed clinically insignificant (<0.5 mm) while nearly all angular discrepancies were considered clinically significant (>2.0°). When the three groups were compared, group C (14-day changes) showed significantly greater accuracy in the posterior segment for maxillary intrusion, distal-crown tip and buccal-crown torque, and mandibular intrusion and extrusion. The mean treatment duration in the 7-day aligner change group was nearly half that of the 14-day aligner change group (5 months vs 9 months).

CONCLUSIONS

Fourteen-day changes were statistically significantly more accurate in some posterior movements. However, this difference in accuracy did not exceed the threshold for clinical significance (>0.5 mm/>2.0°). Achieving a clinically similar accuracy between the 7-day protocol and 14-day protocol in half the treatment time suggests a 7-day protocol as an acceptable treatment protocol. Clinicians may consider slowing down to a 14-day protocol if challenging posterior movements are desired.

A cone-beam computed tomographic study evaluating the efficacy of incisor movement with clear aligners: Assessment of incisor pure tipping, controlled tipping, translation, and torque

INTRODUCTION

This retrospective clinical study aimed to evaluate the efficacy of different types of incisor movements with clear aligners in the sagittal plane.

METHODS

Pretreatment and posttreatment cone-beam computed tomography (CBCT) scans were collected from 69 patients who underwent nonextraction treatment with clear aligners (Invisalign; Align Technology, San Jose, Calif). Integrated 3-dimensional models of the virtual incisor position (ClinCheck; Align Technology) and the posttreatment incisor position (from posttreatment CBCT scans) were superimposed over the pretreatment position (from pretreatment CBCT scans) using Mimics software (Materialise, Leuven, Belgium). On the basis of the location of the rotation center, incisors showing pure tipping (>10°), controlled tipping (>10°), translation (>1 mm), or torque (>10°) movements were selected. Efficacy was determined by comparing the predicted and achieved incisor movement, and differences with efficacy were analyzed using Kruskal-Wallis and Shapiro-Wilk tests (α = 0.05).

RESULTS

In measurements for 231 incisors, the mean efficacy of incisor movements in the sagittal plane was 55.58%. The most and least predictable movements were pure tipping (72.48%) and torque (35.21%), respectively. Labial root movement was significantly more predictable than lingual root movement, and labial movement of the mandibular incisors was significantly easier than that of the maxillary incisors. The type of tooth movement achieved was different from the type designed.

CONCLUSIONS

The efficacy of incisor movement in the sagittal plane using clear aligners varies with designed movement type, and labial root movement appears to be more accurate than the lingual root movement. The biomechanics of clear aligners remains to be further elucidated to achieve more predictable treatment results.

Outcomes of clear aligner treatment with and without Dental Monitoring: A retrospective cohort study

INTRODUCTION

The effects of Invisalign clear aligner treatment with and without Dental Monitoring (DM) were compared for treatment duration, number of appointments, refinements and refinement aligners, and accuracy of Invisalign in achieving predicted tooth positions (aligner tracking). The null hypothesis was that there are no differences between Invisalign with and without DM in these parameters.

METHODS

A sample of 90 consecutively treated Invisalign patients (45 control, 45 DM) fitted the inclusion and exclusion criteria. Treatment duration, number of refinements, number of refinement aligners, time to first refinement, number of appointments, number of emergency visits, and accuracy of predicted tooth movement were observed for differences.

RESULTS

The 2 groups were homogeneous (P >0.05) for sample size, age, gender, Angle classification, maxillary and mandibular irregularity index, and the number of initial aligners. There was a significant (P = 0.001) reduction in the number of appointments by 3.5 visits (33.1%) in the DM group. There was also a significant (P = 0.001) reduction in the time to the first refinement (1.7 months) in the DM group. Compared with Invisalign predicted tooth positions, actual tooth positions were statistically (P <0.05) more accurate for the DM group for the maxillary anterior dentition in rotational movements and mandibular anterior dentition for buccal-lingual linear movement. Invisalign therapy without DM was closer to predicted tooth positions for the maxillary posterior dentition for the tip. None of these differences surpassed the clinically significant thresholds (>0.5 mm or >2°); however, the DM group achieved this in 1.7 fewer months.

CONCLUSIONS

DM with Invisalign therapy resulted in a reduced number of appointments by 3.5 visits (33.1%). The DM group also achieved a clinically similar accuracy in obtaining predicted tooth movements compared with the control group in 1.7 fewer months, indicating improved aligner tracking in the DM group.

Risk Factors of Composite Attachment Loss in Orthodontic Patients during Orthodontic Clear Aligner Therapy: A Prospective Study

BACKGROUND

The composite attachment loss during orthodontic clear aligner therapy is an adverse event that commonly happens in our daily practice. However, there is a lack of related statistical analysis and studies analyzing the related risk factors. Therefore, the aim of this study is to assess the incidence of attachment loss during orthodontic clear aligner therapy and to identify rick factors that may predict such event.

MATERIALS AND METHODS

The demographics and clinical variables of 94 patients undergoing clear aligner therapy (27 males and 67 females; average age: 27.60 ± 0.86 years) were recorded. Both patient-related and tooth-related attachment loss was recorded. The chi-squared test and logistic regressive analysis were applied to identify the potential risk factors. SPSS for Mac (version 23.0, IBM, USA) was used for statistical analyses. P < 0.05 was considered statistically significant.

RESULTS

Our study suggested that the risk factors for attachment loss include frequent aligner removal (≥ 5 times a day) (losing rate = 60.0%, P = 0.005), aligner wear time less than 18 hours a day (losing rate = 50.8%, P = 0.014), eating without aligners inserted (losing rate = 47.9%, P = 0.034), utilizing aligner tray seaters (losing rate = 48.2%, P = 0.006), and unilateral mastication (losing rate = 52.1%, P = 0.002). The multivariable logistic regression analysis indicates that aligner wear time less than 18 hours a day (P = 0.020, B = 0.925), using aligner tray seaters (P = 0.007, B = 1.168), and unilateral mastication (P = 0.034, B = -0.458) were considered independent factors that can predict the composite attachment loss in orthodontic clear aligner therapy.

CONCLUSION

Wearing aligner less than 18 hours a day, using aligner tray seaters, and unilateral mastication may contribute to increased incidence of composite attachment loss during orthodontic clear aligner therapy.

The application of 3D metrology software in the quantitative and qualitative assessment of aligner treatment outcomes

3D metrology software (Geomagic® Control X™) can be used in orthodontic treatment to significantly improve the analysis of achieved tooth movements compared with those predicted by treatment planning software, such as ClinCheck® software (Align Technology®). The applications of this technology enable clinicians to present more accurate and detailed case presentations and analyse their treatment outcomes. Additionally, information presented may further aid clinicians in interpreting and understanding metrology-derived information, in the form of digital heat maps, when incorporated into case presentations and scientific articles.

Quantitative assessment of interproximal tooth reduction performed as part of Invisalign® treatment in 10 orthodontic practices

Background

Interproximal reduction (IPR) is a treatment option for orthodontic space gain. The attainment of prescribed objectives in aligner treatment may require IPR that is accurately performed both qualitatively and quantitatively.

Objective

This study assesses the in vivo accuracy of IPR carried out in 10 orthodontic practices as a method of orthodontic space creation.

Methods

A comparison of proposed and achieved amounts of IPR completed (accuracy), the accuracy of IPR within and between upper and lower dental arches, and the accuracy of IPR within and between posterior and anterior arch segments were performed using 3-dimensional digital study models gained via Align’s® ClinCheck.

Results

The findings indicated that IPR was routinely underperformed by all practices studied. On average, the amount of IPR achieved represented only 44.0% of the total prescribed per tooth in the sample assessed, with a mean discrepancy of 0.16 mm per tooth. There were statistically significant differences only between the overall anterior and posterior groups (p < 0.01) and between maxillary anterior and maxillary posterior groups (p < 0.01); however, these were not clinically significant. Significant differences in IPR performance were noted between different orthodontic practices.

Conclusions

This study demonstrates that the clinical performance of IPR in 10 orthodontic practices consistently fails to achieve the prescribed amount often by large variations. The effect of this under-performance on clinical outcomes remains to be quantified.

Virtual occlusion in orthognathic surgery

The aim of this retrospective study was to determine whether a virtually created occlusion is as accurate as a conventionally created occlusion. Seventeen orthognathic patients were included in the study, which was conducted in a university clinic. Plaster cast models were obtained and digitized. Two experienced observers created the conventional (gold standard) and virtual occlusion to assess inter-observer variability. One observer created the conventional and virtual occlusion a second time to assess the intra-observer variability. The criterion for accepting the virtual occlusion was that the difference between the gold standard and the virtual occlusion was not larger than the intra-observer variability for the gold standard. A non-parametric Kruskal-Wallis H test was performed to detect statistically significant differences between the intra- and inter-observer groups for both the conventional and virtual occlusion. No statistically significant differences were found between the different groups. The difference between the conventional and virtual occlusion group was 0.20mm larger than the intra-observer variability of the gold standard. The virtual occlusion tool presented here can be utilized in daily clinical practice and makes the use of physical dental models redundant.

Arch expansion with the Invisalign system: Efficacy and predictability

Background

In adult patients, treatment of skeletal crossbite requires combined treatment by fixed or removable appliances and orthognathic surgery. In cases of dentoalveolar crossbite, expansion can be achieved with fixed multibrackets and removable transparent aligners. Various researchers have already assessed the Invisalign system’s predictability for arch expansion. However, most of this research was conducted using older appliances, making it necessary to assess the characteristics of the updated system SmartTrack.

Material and methods

A sample of 114 patients with transverse malocclusion were treated with SmartTrack. The predictability of the system’s software (Clincheck) was assessed by comparing planned measurements (width of canines, premolars and molars rotations and inclinations) with the real measurements achieved at the end of the first treatment phase. Measurements were imported to Clincheck software to create three data sets; T1: initial measurements at start of treatment; T2: Clincheck predicted measurements at end of first treatment phase; T3: measurements taken at start of the second treatment phase.

Results

Widths underwent significant advances as a result of treatment. For all widths, virtual planning obtained prognoses of greater expansion than actually achieved: a mean of 0.63 mm more expansion at the canine level (p<0.001), 0.77 mm at first premolar (p<0.001), 0.81 at second premolar (p<0.001), 0.69 mm at first molar (p<0.001), and 0.25 mm at second molar (p = 0.183). All the treatment plan’s estimations, with the exception of the second molar, were significantly higher than the actual outcomes.

Conclusions

Aligners are an effective tool for producing arch expansion, being more effective in premolar area and less effective in canine and second molar area. Predictability was reasonable for expansion movement. Overcorrection should be considered at the virtual planning stage in order to obtain the expected outcomes.

Clinical follow-up of corticotomy-accelerated Invisalign orthodontic treatment with Dental Monitoring

The demand for fast and invisible treatment options for adults has grown. Treatment protocols involving clear aligners in association with alveolar corticotomy have been developed in response to this demand. Alveolar corticotomy surgery can accelerate orthodontic tooth movement, but good clinical follow-up is crucial and can become cumbersome as the frequency of aligner changes accelerates. Clinical monitoring with patient-managed software can be of assistance in such cases. We present the ortho-surgical treatment of a healthy 21-year-old woman with Class III malocclusion who was treated with corticotomy-accelerated presurgical decompensation and clear aligners, followed by mandibular sagittal split osteotomy. Alveolar corticotomy surgery was performed and the aligners were changed every 4 days. Clinical follow-up of aligner-mediated tooth movement was managed with a patient-managed smartphone application, allowing early interception and correction of minute orthodontic movement errors. Such errors would have been difficult to detect considering the rapidity of aligner change when accelerated by alveolar corticotomy. Clinical follow-up with a patient-managed smartphone application could thus allow for better and easier management of corticotomy-accelerated clear aligner orthodontic treatment.

Accuracy of interproximal enamel reduction during clear aligner treatment

Aim

The aim of the present study was to compare the accuracy of the actual space obtained through interproximal enamel reduction (IPR) compared to the amount of IPR planned through the digital setup during clear aligner treatment (CAT).

Materials and methods

A total of 10 clinicians were randomly recruited using the Doctor Locator by Align Technology (California). For each clinician, four consecutive patients treated with CAT and manual stripping were selected for a total of 40 subjects and 80 dental arches. For each patient, the amount of planned IPR and the amount of actual IPR performed were recorded. Each arch was considered individually. For each arch, the mesio-distal tooth measurements were obtained from second to second premolars.

Results

No systematic measurement errors were identified. In 25 cases, stripping was planned and performed in both arches; in 4 cases only in the upper arch and in the remaining 7 cases only in the lower arch. The difference between planned IPR and performed IPR was on average 0.55 mm (SD, 0.67; P = 0.022) in the upper arch and 0.82 mm (SD, 0.84; P = 0.026) in the lower arch. The accuracy of IPR in the upper arch was estimated to be 44.95% for the upper arch and 37.02% for the lower arch.

Conclusion

Overall, this study showed that the amount of enamel removed in vivo did not correspond with the amount of IPR planned. In most cases, the performed IPR amount was lower than planned. When considering the actual amount in millimeter, these differences may not be considered clinically relevant.

Has Invisalign improved? A prospective follow-up study on the efficacy of tooth movement with Invisalign

INTRODUCTION

The purpose of this research was to provide an update on the accuracy of tooth movement with Invisalign (Align Technology, Santa Clara, Calif).

METHODS

This prospective clinical study included 38 patients treated with Invisalign Full or Invisalign Teen. All teeth, from the central incisor to the second molar, were measured on digital models created from intraoral scans. Predicted values were determined by superimposing the initial and final ClinCheck models, and achieved values were determined by superimposing the initial ClinCheck models and the digital models from the posttreatment scans. Individual teeth were superimposed with a best-fit analysis and measured using Compare software (version 8.1; GeoDigm, Falcon Heights, Minn). The types of tooth movements studied were a mesial-distal crown tip, buccal-lingual crown tip, extrusion, intrusion, and mesial-distal rotation.

RESULTS

The mean accuracy of Invisalign for all tooth movements was 50%. The highest overall accuracy was achieved with a buccal-lingual crown tip (56%), whereas the lowest overall accuracy occurred with rotation (46%). The accuracies for mesial rotation of the mandibular first molar (28%), distal rotation of the maxillary canine (37%), and intrusion of the mandibular incisors (35%) were particularly low.

CONCLUSIONS

There was a marked improvement in the overall accuracy; however, the strengths and weaknesses of tooth movement with Invisalign remained relatively the same.

Bimaxillary protrusion and gummy smile treated with clear aligners: Closing premolar extraction spaces with bone screw anchorage

Inadequate posterior anchorage is a serious limitation for aligner treatment involving extraction of four first premolars. Inappropriate axial inclinations may compromise intermaxillary occlusion and stability. OrthoBoneScrew® (OBS) anchorage is designed to augment the Invisalign® clear aligner G6 solution to produce more predictable outcomes as illustrated by the current case report. An 18-year-old female presented with two chief complains: (1) Protrusive, incompetent lips, and (2) excessive gingival exposure when smiling (“gummy smile”). Clinical evaluation revealed bimaxillary protrusion, hypermentalis activity, anterior crowding, and excessive anterior axial inclinations, particularly of the lower incisors (116°). The American Board of Orthodontic (ABO) discrepancy index (DI) was 21. The treatment plan was extraction of all four first premolars, and clear aligner (Invisalign®) therapy anchored with four OBSs: Infra-zygomatic crest (IZC), and between the roots of the upper central and lateral incisors (Incisal) bilaterally. Eighteen months of initial treatment with 45 aligners retracted and intruded the anterior segments in both arches by closing the extraction spaces with supplemental anchorage provided by IZC and Incisal OBSs. The final series of 20 refinement aligners achieved an excellent outcome as evidenced by an ABO cast-radiograph evaluation (CRE) score of 10, and a pink and white (P&W) dental esthetic score of 3. Post-treatment analysis revealed multiple opportunities for improvement. The patient was well satisfied with the final outcome.

Effectiveness of clear aligner therapy for orthodontic treatment: A systematic review

OBJECTIVE

To analyse through a systematic review the effectiveness of clear aligners by assessing: (a) predictability of clear aligners and (b) treatment outcome comparison of clear aligner therapy with fixed appliance therapy.

METHODS

An electronic search was made from January 2014 to April 2019 using MEDLINE, Embase, Web of Science and LILACS databases without any limitations on language. Three reviewers independently assessed the articles. Quality assessment of observational studies and randomized control trial was done by using the ROBINS tool and Cochrane risk of bias tool, respectively. GRADE instrument was used to assess certainty level for each identified outcome.

RESULTS

Seven eligible articles (one randomized controlled trial and six retrospective cohort) were included in our systematic review. Most of the studies (six out of seven) had a moderate risk of bias and one had a high risk of bias.

CONCLUSIONS

'Low to moderate level' of certainty in regard to specific clear aligner therapy tooth movements' efficiency was identified. Clear aligners may produce clinically acceptable outcomes that could be comparable to fixed appliance therapy for buccolingual inclination of upper and lower incisors in mild to moderate malocclusions. However, not all potential clinical scenarios have been assessed in the included studies. Most of the tooth movements may not be predictable enough to be accomplished with only one set of trays with clear aligners despite the recent advances in technology.

Virtual setup in orthodontics: planning and evaluation

OBJECTIVES

The purpose of this study was to evaluate the clinical accuracy of virtual orthodontic setups by using a new CBCT-based approach.

MATERIALS AND METHODS

Ten patients who underwent pre-surgical orthodontics were included in this study. Pre-treatment and pre-surgical cone-beam CT (CBCT) scans and digital dental models were available. The pre-treatment digital dental model was used to create an orthodontic virtual setup. The digital dental models were fused with the corresponding CBCT scans, and the two CBCT scans were aligned using voxel-based matching. Moving each individual tooth from the virtual setup to the final outcome allows the calculation of the accuracy of the virtual setup by using an iterative closest point algorithm. Differences between virtual setup and final outcome were recorded as well as the ICC between two observers.

RESULTS

The inter-observer variability showed a high level of agreement between the observers. The largest mean difference between observers was found in the cranial/caudal direction (0.36 ± 0.30 mm) and the roll rotation (1.54 ± 0.98°). Differences between the virtual setup and final outcome were small in the translational direction (0.45 ± 0.48 mm). Rotational mean differences were larger with the pitch of the incisors (0.00 ± 7.97°) and molars (0.01 ± 10.26°) as largest difference. Excessive extrusion of all upper teeth and more anterior movement than planned were seen for both upper and lower arch. Lower molars showed less extrusion.

CLINICAL RELEVANCE

The data of this study can be used to obtain more insight in the accuracy and achievability of orthodontic virtual setup. Tooth movement can now be studied in more details which can lead to new insights.